1. Field of the Invention
The present invention relates to a surface mount circularly polarized wave antenna and a communication apparatus using the same, and more particularly, to a surface mount circularly polarized wave antenna for use in a system using circularly polarized radio waves such as GPS, DAB, ETC, and the like, and a communication apparatus using the same.
2. Description of the Related Art
In recent years, there have been applied more different types of systems using circularly polarized radio waves such as GPS (Global Positioning System), DAB (Digital Audio Broadcasting), ETC (Electric Toll Collection), and the like. With the increase of such systems in number, it has been required more intensively to develop miniaturized antennas suitable for use in communication apparatuses of the systems and adapted to use with circularly polarized waves.
FIG. 10 shows one example of conventional circularly polarized wave antennas. The antenna of FIG. 10 is a square patch antenna. The circularly polarized wave antenna 1 shown in FIG. 10 comprises a ground electrode 3 disposed substantially on the whole of a first main face of a substrate 2 made of a dielectric and having a flat plate shape, a radiation electrode 4 having a substantially rectangular shape disposed on a second main face, and a feeding line 5 so provided as to go through the substrate 2 from the first main face to be connected to the radiation electrode 4. Six fixing electrodes 6 for soldering are disposed on side faces of the substrate 2. The fixing electrodes 6 are connected to the ground electrode 3. The feeding line 5 is insulated from the ground electrode 3 in the first main face of the substrate 2. The node between the radiation electrode 4 and the feeding line 5 is set at an appropriate position between the center of the radiation electrode 4 and one corner thereof. The radiation electrode 4 is so sized that each side of the electrode 4 has a length substantially equal to one half of the effective wavelength at a frequency applicable to the antenna. Furthermore, degeneracy separation elements 4a are provided in two diagonal opposite corners of the radiation electrode 4 (in this case, the elements are realized by forming a taper in the corners).
According to the circularly polarized wave antenna 1 configured as described above, a signal, input to the radiation electrode 4 through the feeding line 5, causes two resonant currents, which are perpendicular to each other and having a phase difference of 90.degree., to be generated in the radiation electrode 4. From the two resonant currents, a circularly polarized wave is radiated mainly in the normal direction of the radiation electrode 4.
However, the circularly polarized wave antenna 1 shown in FIG. 10 is so configured that the feeding line 5 goes through the substrate 2 from the first main face to the second main face. Therefore, there are problems that the surface mounting is difficult, and the mounting cost is increased.